Li2O-Al2O3-SiO2-BASED CRYSTALLIZED GLASS

ABSTRACT

A Li 2 O—Al 2 O 3 —SiO 2 -based crystallized glass contains: in a mass basis, SnO 2 : 0% to 5%; and HfO 2 +Ta 2 O 5 : 0.01% to 10%.

TECHNICAL FIELD

The present invention relates to a Li₂O—Al₂O₃—SiO₂-based crystallized glass. Specifically, the present invention relates to a Li₂O—Al₂O₃—SiO₂-based crystallized glass suitable as a material for, for example, front windows of oil stoves or wood stoves, substrates for high-tech products such as substrates for color filters and image sensors, setters for firing electronic components, light diffusers, core tubes for semiconductor manufacturing, semiconductor manufacturing masks, optical lenses, dimensional measurement members, communication members, building members, chemical reaction containers, top plates for electromagnetic cooking, and window glass for fire doors.

BACKGROUND ART

In the related art, a Li₂O—Al₂O₃—SiO₂-based crystallized glass is used as a material for, for example, front windows of oil stoves or wood stoves, substrates for high-tech products such as substrates for color filters and image sensors, setters for firing electronic components, top plates for electromagnetic cooking, and window glass for fire doors. For example, Patent Literatures 1 to 3 disclose a Li₂O—Al₂O₃—SiO₂-based crystallized glass obtained by precipitating a Li₂O—Al₂O₃—SiO₂-based crystal such as a β-quartz solid solution (Li₂O—Al₂O₃.nSiO₂ [where 2≤n≤4]) and a β-spodumene solid solution (Li₂O.Al₂O₃.nSiO₂ [where n≥4]) as a main crystal.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass has excellent thermal properties because of having a low thermal expansion coefficient and high mechanical strength. When heat treatment conditions in a crystallization step are appropriately adjusted, it is possible to control the type of precipitated crystals, and a transparent crystallized glass (β-quartz solid solution is precipitated) can be easily produced.

However, when manufacturing this type of crystallized glass, melting at a high temperature higher than 1,400° C. is required. Therefore, as a fining agent to be added to a glass batch, As₂O₃ and Sb₂O₃, which can generate a large amount of fining gas in the melting at a high temperature, are used. However, As₂O₃ and Sb₂O₃ are highly toxic and may pollute the environment during a glass manufacturing step or a waste glass treatment.

Therefore, SnO₂ and Cl have been proposed as alternative fining agents for As₂O₃ and Sb₂O₃ (see, for example, Patent Literatures 4 and 5). However, Cl easily corrodes a mold and a metal roll during glass molding, and as a result, the surface quality of the glass may be deteriorated. From such a viewpoint, it is preferable to use SnO₂ as the fining agent, which does not cause the above problems.

CITATION LIST Patent Literature

-   Patent Literature 1: JP-B-S39-21049 -   Patent Literature 2: JP-B-S40-20182 -   Patent Literature 3: JP-A-H01-308845 -   Patent Literature 4: JP-A-H11-228180 -   Patent Literature 5: JP-A-H11-228181

SUMMARY OF INVENTION Technical Problem

As described above, SnO₂ is a preferred component from the viewpoint of not polluting the environment. However, as described in Patent Literatures 4 and 5, since SnO₂ has an effect of strengthening the coloring caused by TiO₂, Fe₂O₃, etc., there is a problem that the yellowish color of the transparent crystallized glass is strengthened, which is not preferred in appearance.

An object of the present invention is to provide a Li₂O—Al₂O₃—SiO₂-based crystallized glass in which yellow coloring caused by TiO₂, Fe₂O₃, etc. is prevented.

Solution to Problem

When improving the yellow coloring of the transparent crystallized glass caused by TiO₂, Fe₂O₃, etc., it is sufficient to reduce the contents of these components. However, in particular, when the content of TiO₂ is reduced, the optimum firing temperature range is narrowed, and the amount of crystal nuclei produced tends to be reduced. As a result, the number of coarse crystals increases, the crystallized glass becomes cloudy, and the transparency tends to be impaired. However, it has been found that the shortage of the amount of crystal nuclei produced due to the reduction of the content of TiO₂ can be compensated by containing either HfO₂ or Ta₂O₅, and since the transparent crystallized glass containing either HfO₂ or Ta₂O₅ emits blue light by ultraviolet light, it is possible to prevent yellow coloring.

A Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention contains: in a mass basis, SnO₂: 0% to 5%; and HfO₂+Ta₂O₅: 0.01% to 10%. Accordingly, it is easy to obtain a Li₂O—Al₂O₃—SiO₂-based crystallized glass in which coloring of the glass and precipitation of coarse crystals are prevented and which has excellent transparency. Here, the expression “HfO₂+Ta₂O₅” means the total amount of the contents of HfO₂ and Ta₂O₅.

A Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention preferably contains: in a mass basis, SiO₂: 40% to 90%; Al₂O₃: 5% to 30%; Li₂O: 1% to 10%; SnO₂: 0.01% to 5%; and HfO₂+Ta₂O₅: 0.01% to 10%.

A Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention preferably contains: in a mass basis, SiO₂: 40% to 90%; Al₂O₃: 5% to 30%; Li₂O: 1% to 10%; SnO₂: 0.01% to 5%; and HfO₂+Ta₂O₅: 0.05% to 10%.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention preferably further contains: in a mass basis, Na₂O: 0% to 10%; K₂O: 0% to 10%; MgO: 0% to 10%; CaO: 0% to 10%; SrO: 0% to 10%; BaO: 0% to 10%; ZnO: 0% to 10%; P₂O₅: 0% to 5%; TiO₂: 0% to 2%, and ZrO₂: 0% to 10%.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention preferably has a colorless and transparent appearance.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention preferably has a transmittance of 10% or more at a thickness of 3 mm and a wavelength of 300 nm. Accordingly, the Li₂O—Al₂O₃—SiO₂-based crystallized glass can be suitably used for various applications that require ultraviolet transparency.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, a β-quartz solid solution is preferably precipitated as a main crystal. Accordingly, a crystallized glass having a low thermal expansion coefficient can be easily obtained.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, a thermal expansion coefficient thereof at 30° C. to 380° C. is preferably 20×10⁻⁷/° C. or less. Accordingly, the Li₂O—Al₂O₃—SiO₂-based crystallized glass can be suitably used for various applications that require low expansibility.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, a thermal expansion coefficient thereof at 30° C. to 750° C. is preferably 25×10⁻⁷/° C. or less. Accordingly, the Li₂O—Al₂O₃—SiO₂-based crystallized glass can be suitably used for various applications that require low expansibility at a wider temperature range.

A Li₂O—Al₂O₃—SiO₂-based crystallizable glass according to the present invention contains: in a mass basis, SnO₂: 0% to 5%; and HfO₂+Ta₂O₅: 0.01% to 10%.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a Li₂O—Al₂O₃—SiO₂-based crystallized glass in which yellow coloring caused by TiO₂, Fe₂O₃, etc. is prevented.

DESCRIPTION OF EMBODIMENTS

A Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention contains, in a mass basis, SnO₂: 0% to 5% and HfO₂+Ta₂O₅: 0.01% to 10%, and preferably contains, in a mass basis, SiO₂: 40% to 90%, Al₂O₃: 5% to 30%, Li₂O: 1% to 10%, SnO₂: 0.01% to 5%, and HfO₂+Ta₂O₅: 0.01% to 10%. The reasons for limiting the glass composition as described above are shown below. In the following description of the content of each component, “%” means “mass %” unless otherwise specified.

SiO₂ is a component that forms a glass skeleton and constitutes a Li₂O—Al₂O₃—SiO₂-based crystal. The content of SiO₂ is preferably 40% to 90%, 50% to 85%, 52% to 83%, 55% to 80%, 55% to 75%, 55% 73%, 55% to 71%, 56% to 70%, 57% to 70%, 58% to 70%, 59% to 70%, and particularly preferably 60% to 70%. When the content of SiO₂ is too small, the thermal expansion coefficient tends to be high, and it is difficult to obtain a crystallized glass having excellent thermal shock resistance. In addition, the chemical durability tends to be lowered. On the other hand, when the content of SiO₂ is too large, the meltability of the glass is lowered, the viscosity of the glass melt is increased, it is difficult to fine the glass, the molding of the glass is difficult, and the productivity tends to be lowered.

Al₂O₃ is a component that forms a glass skeleton and constitutes a Li₂O—Al₂O₃—SiO₂-based crystal. The content of Al₂O₃ is preferably 5% to 30%, 7% to 30%, 8% to 29%, 10% to 28%, 13% to 27%, 15% to 26%, 16% to 26%, 17% to 25%, 17% to 24%, 18% to 24%, 19% to 24%, and particularly preferably 20% to 23%. When the content of Al₂O₃ is too small, the thermal expansion coefficient tends to be high, and it is difficult to obtain a crystallized glass having excellent thermal shock resistance. In addition, the chemical durability tends to be lowered. On the other hand, when the content of Al₂O₃ is too large, the meltability of the glass is lowered, the viscosity of the glass melt is increased, it is difficult to fine the glass, the molding of the glass is difficult, and the productivity tends to be lowered. In addition, mullite crystals tend to precipitate, the glass tends to be devitrified, and the glass is easily broken.

Li₂O is a component that constitutes a Li₂O—Al₂O₃—SiO₂-based crystal, and is a component that has a great influence on crystallinity and lowers the viscosity of the glass to improve the meltability and formability of the glass. The content of Li₂O is preferably 1% to 10%, 2% to 10%, 2% to 9%, 2% to 8%, 2% to 7%, 2.5% to 6%, 2.5% to 5%, 3% to 4.5%, and particularly preferably 3% to 4%. When the content of Li₂O is too small, mullite crystals tend to precipitate and the glass tends to be devitrified. In addition, when crystallizing the glass, a Li₂O—Al₂O₃—SiO₂-based crystal is less likely to precipitate, and it is difficult to obtain a crystallized glass having excellent thermal shock resistance. Further, the meltability of the glass is lowered, the viscosity of the glass melt is increased, it is difficult to fine the glass, the molding of the glass is difficult, and the productivity tends to be lowered. On the other hand, when the content of Li₂O is too large, the crystallinity becomes too strong, the glass tends to be devitrified, and the glass is easily broken.

SnO₂ is a component that acts as a fining agent. When SnO₂ is used as a fining agent, the glass can be sufficiently fined without using a highly toxic fining agent As₂O₃ or Sb₂O₃. SnO₂ is also a component that serves as a nucleating agent for precipitating a crystal in a crystallization step. On the other hand, SnO₂ is also a component that remarkably strengthens the coloring of the glass when contained in a large amount. The content of SnO₂ is preferably 0% to 5%, 0.01% to 5%, 0.01% to 4%, 0.02% to 3%, 0.03% to 2.5%, 0.05% to 3%, 0.05% to 2.5%, 0.05% to 2%, 0.05% to 1.9%, 0.05% to 1.8%, 0.05% to 1.7%, 0.05% to 1.6%, 0.05% to 1.5%, 0.1% to 1%, 0.1% to 0.5%, 0.1% to 0.4%, 0.1% to 0.35%, and particularly preferably 0.15% to 0.25%. When the content of SnO₂ is too small, it is difficult to fine the glass, and the productivity tends to be lowered. On the other hand, when the content of SnO₂ is too large, the coloring of the glass is increased.

HfO₂ and Ta₂O₅ are components that serve as a nucleating agent for precipitating a crystal in the crystallization step. HfO₂ and Ta₂O₅ are also components that emit blue light by ultraviolet light, which serve as a complementary color and prevent yellow coloring. The content of HfO₂+Ta₂O₅ is preferably 0.01% to 10%, 0.02% to 10%, 0.03% to 10%, 0.04% to 10%, 0.05% to 10%, 0.06% to 10%, 0.07% to 10%, 0.08% to 10%, 0.09% to 9%, 0.1% to 8%, 0.11% to 7%, 0.12% to 6%, 0.5% to 5%, 1% to 4%, 2% to 3.5%, and particularly preferably 3% to 3.5%. When the content of HfO₂+Ta₂O₅ is too small, crystal nuclei may not be sufficiently formed, and coarse crystals may precipitate to cause the glass to become cloudy or broken. In addition, the coloring of the glass tends to increase. On the other hand, when the content of HfO₂+Ta₂O₅ is too large, the glass tends to be devitrified in melting, making it difficult to mold the glass and reducing the productivity. The content of each component, i.e., HfO₂ and Ta₂O₅, is preferably 0.01% to 10%, 0.02% to 10%, 0.03% to 10%, 0.04% to 10%, 0.05% to 10%, 0.06% to 10%, 0.07% to 10%, 0.08% to 10%, 0.09% to 9%, 0.1% to 8%, 0.11% to 7%, 0.12% to 6%, 0.5% to 5%, 1% to 4%, 2% to 3.5%, and particularly preferably 3% to 3.5%. HfO₂ and Ta₂O₅ may be mixed as impurities.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention may contain the following components in a glass composition, in addition to the above components.

Na₂O is a component that solid-dissolves in a Li₂O—Al₂O₃—SiO₂-based crystal, and is a component that has a great influence on crystallinity and lowers the viscosity of the glass to improve the meltability and formability of the glass. The content of Na₂O is preferably 0% to 10%, 0% to 9.5%, 0% to 9%, 0% to 8.5%, 0% to 8%, 0% to 7.5%, 0% to 7%, 0% to 6.5%, 0% to 6%, 0% to 5.5%, 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0% to 1%, and particularly preferably 0.1% to 0.8%. When the content of Na₂O is too large, the crystallinity becomes too strong, the glass is easily devitrified, and the glass is easily broken.

K₂O is a component that solid-dissolves in a Li₂O—Al₂O₃—SiO₂-based crystal, and is a component that has a great influence on crystallinity and lowers the viscosity of the glass to improve the meltability and formability of the glass. The content of K₂O is preferably 0% to 10%, 0% to 9.5%, 0% to 9%, 0% to 8.5%, 0% to 8%, 0% to 7.5%, 0% to 7%, 0% to 6.5%, 0% to 6%, 0% to 5.5%, 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0% to 1%, and particularly preferably 0.1% to 0.8%. When the content of K₂O is too large, the crystallinity becomes too strong, the glass is easily devitrified, and the glass is easily broken.

MgO is a component that solid-dissolves in a Li₂O—Al₂O₃—SiO₂-based crystal and increases the thermal expansion coefficient of the Li₂O—Al₂O₃—SiO₂-based crystal. The content of MgO is preferably 0% to 10%, 0% to 9.5%, 0% to 9%, 0% to 8.5%, 0% to 8%, 0% to 7.5%, 0% to 7%, 0% to 6.5%, 0% to 6%, 0% to 5.5%, 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0.1% to 2%, and particularly preferably 0.3% to 1.5%. When the content of MgO is too large, the crystallinity becomes too strong, the glass is easily devitrified, and the glass is easily broken. In addition, the thermal expansion coefficient tends to be too high.

CaO is a component that lowers the viscosity of the glass to improve the meltability and formability of the glass. The content of CaO is preferably 0% to 10%, 0% to 9.5%, 0% to 9%, 0% to 8.5%, 0% to 8%, 0% to 7.5%, 0% to 7%, 0% to 6.5%, 0% to 6%, 0% to 5.5%, 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0% to 2%, and particularly preferably 0% to 1%. When the content of CaO is too large, the glass is easily devitrified, and the glass is easily broken.

SrO is a component that lowers the viscosity of the glass to improve the meltability and formability of the glass. The content of SrO is preferably 0% to 10%, 0% to 9.5%, 0% to 9%, 0% to 8.5%, 0% to 8%, 0% to 7.5%, 0% to 7%, 0% to 6.5%, 0% to 6%, 0% to 5.5%, 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0% to 2%, and particularly preferably 0% to 1%. When the content of SrO is too large, the glass is easily devitrified, and the glass is easily broken.

BaO is a component that lowers the viscosity of the glass to improve the meltability and formability of the glass. The content of BaO is preferably 0% to 10%, 0% to 9.5%, 0% to 9%, 0% to 8.5%, 0% to 8%, 0% to 7.5%, 0% to 7%, 0% to 6.5%, 0% to 6%, 0% to 5.5%, 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0.1% to 2%, 0.5% to 1.8%, and particularly preferably 1% to 1.5%. When the content of BaO is too large, crystals containing Ba are precipitated, the glass is easily devitrified, and the glass is easily broken.

ZnO is a component that solid-dissolves in a Li₂O—Al₂O₃—SiO₂-based crystal and has a great influence on crystallinity. The content of ZnO is preferably 0% to 10%, 0% to 9.5%, 0% to 9%, 0% to 8.5%, 0% to 8%, 0% to 7.5%, 0% to 7%, 0% to 6.5%, 0% to 6%, 0% to 5.5%, 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0% to 2%, 0% to 1%, and particularly preferably 0% to 0.6%. When the content of ZnO is too large, the crystallinity becomes too strong, the glass is easily devitrified, and the glass is easily broken.

P₂O₅ is a component that prevents the precipitation of a coarse ZrO₂-based crystal. The content of P₂O₅ is preferably 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, 0% to 3%, 0% to 2.5%, 0% to 2%, 0.5% to 2%, 1% to 2%, and particularly preferably 1.2% to 1.8%. When the content of P₂O₅ is too large, the precipitation amount of the Li₂O—Al₂O₃—SiO₂-based crystal tends to be small, and the thermal expansion coefficient tends to be high.

TiO₂ is a component that serves as a nucleating agent for precipitating a crystal in the crystallization step. On the other hand, TiO₂ is also a component that remarkably strengthens the coloring of the glass when contained in a large amount, particularly a component that remarkably strengthens the coloring by interacting with SnO₂. In addition, when Ti remains in the residual glass phase, LMCT transition may occur from the valence band of the SiO₂ skeleton to the conduction band of tetravalent Ti of the residual glass phase. Further, in the trivalent Ti of the residual glass phase, d-d transition occurs, which is involved in the coloring of the crystallized glass. Further, it is known that when Ti and Fe coexist, ilmenite (FeTiO₃)-like coloring is exhibited, and when Ti and Sn coexist, the yellowish color is strengthened. Therefore, the content of TiO₂ is preferably 0% to 2%, 0% to 1%, 0% to 0.5%, 0% to 0.4%, 0% to 0.3%, 0% to 0.2%, and particularly preferably 0% to 0.1%. However, since TiO₂ is mixed as an impurity, when it is attempted to completely remove TiO₂, the raw material batch is expensive and the manufacturing cost tends to increase. In order to prevent the increase in manufacturing cost, the lower limit of the content of TiO₂ is preferably 0.0003% or more, 0.0005% or more, 0.001% or more, 0.005% or more, 0.01% or more, and particularly preferably 0.02% or more.

ZrO₂ is a nucleation component for precipitating a crystal in the crystallization step. The content of ZrO₂ is preferably 0% to 10%, 0% to 5%, 0.1% to 4%, 0.2% to 4%, 0.3% to 4%, 0.4% to 4%, 0.5% to 4%, 0.5% to 3.9%, 0.5% to 3.8%, 0.5% to 3.7%, 0.5% to 3.6%, 0.5% to 3.5%, 0.5% to 3.4%, 0.5% to 3.3%, 0.5% to 3.2%, 0.6% to 3.2%, 0.7% to 3.2%, 0.8% to 3.2%, 0.9% to 3.2%, 1% to 3.2%, 1.1% to 3.2%, 1.2% to 3.2%, 1.3% to 3.2%, 1.4% to 3.2%, 1.5% to 3.2%, 1.6% to 3.2%, 1.7% to 3.2%, 1.7% to 3%, 1.7% to 2.8%, and particularly preferably 2% to 2.5%. When the content of ZrO₂ is too large, coarse ZrO₂ crystals are precipitated, the glass is easily devitrified, and the glass is easily broken.

Fe₂O₃ is a component that strengthens the coloring of the glass, particularly a component that remarkably strengthens the coloring by interacting with SnO₂. The content of Fe₂O₃ is preferably 0% to 0.05%, 0% to 0.03%, 0% to 0.01%, 0% to 0.005%, 0% to 0.004%, 0% to 0.003%, and particularly preferably 0% to 0.002%. However, since Fe₂O₃ is mixed as an impurity, when it is attempted to completely remove Fe₂O₃, the raw material batch is expensive and the manufacturing cost tends to increase. In order to prevent the increase in manufacturing cost, the lower limit of the content of Fe₂O₃ is preferably 0.0001% or more, 0.0002% or more, 0.0003% or more, 0.0005% or more, and particularly preferably 0.001% or more.

As₂O₃ and Sb₂O₃ are highly toxic and may pollute the environment during a glass manufacturing step or a waste glass treatment. Therefore, it is preferable that the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention does not substantially contain these components (specifically, less than 0.1 mass %).

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention may contain a trace component such as H₂, CO₂, CO, H₂O, He, Ne, Ar, or N₂ up to 0.1% respectively, in addition to the above components. In addition, the glass may contain up to 10 ppm of a noble metal element such as Ag, Au, Pd or Ir respectively.

Further, the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention may contain Pt, Rh, B₂O₃, Cr₂O₃, SO₃, MnO, CeO₂, Cl₂, Y₂O₃, MoO3, La₂O₃, WO₃, Nd₂O₃, Nb₂O₅, Sc₂O₃, V₂O₅, RfO₂ and the like in a total amount of up to 10% as long as there is no adverse influence on coloring.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention having the above composition tends to be colorless and transparent in appearance.

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention preferably has a transmittance of 10% or more, 20% or more, and particularly preferably 30% or more at a thickness of 3 mm and a wavelength of 300 nm. When the transmittance is too low, the yellow coloring of the glass becomes too strong and the transparency of the glass is lowered. When either HfO₂ or Ta₂O₅ is used as the nucleating agent, the glass emits blue light and the yellow coloring can be prevented, so that the transmittance can be easily increased.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, a β-quartz solid solution is preferably precipitated as a main crystal. If the β-quartz solid solution is precipitated as the main crystal, the crystallized glass easily transmits visible light and the transparency is easily increased. In addition, it is easy to bring the thermal expansion coefficient of the glass close to zero. When either HfO₂ or Ta₂O₅ is used as the nucleating agent, the amount of the β-quartz solid solution precipitated can be controlled, and it is easier to bring the thermal expansion coefficient of the glass close to zero. A white opaque crystallized glass in which a β-spodumene solid solution is precipitated as the main crystal may be used.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, the thermal expansion coefficient at 30° C. to 380° C. is preferably 20×10⁻⁷/° C. or less, 18×10⁻⁷/° C. or less, 15×10⁻⁷/° C. or less, 14×10⁻⁷/° C. or less, 13×10⁻⁷/° C. or less, 12×10⁻⁷/° C. or less, 11×10⁻⁷/° C. or less, 10×10⁻⁷/° C. or less, 9×10⁻⁷/° C. or less, 8×10⁻⁷/° C. or less, 7×10⁻⁷/° C. or less, 6×10⁻⁷/° C. or less, 5×10⁻⁷/° C. or less, 4×10⁻⁷/° C. or less, 3×10⁻⁷/° C. or less, and particularly preferably 2×10⁻⁷/° C. or less. The lower limit of the thermal expansion coefficient at 30° C. to 380° C. is not particularly limited, and is practically −30×10⁻⁷/° C. or more. When dimensional stability and/or thermal shock resistance is specifically required, the thermal expansion coefficient at 30° C. to 380° C. is preferably −5×10⁻⁷/° C. to 5×10⁻⁷/° C., −3×10⁻⁷/° C. to 3×10⁻⁷/° C., −2.5×10⁻⁷/° C. to 2.5×10⁻⁷/° C., −2×10⁻⁷/° C. to 2×10⁻⁷/° C., −1.5×10⁻⁷/° C. to 1.5×10⁻⁷/° C., −1×10⁻⁷/° C. to 1×10⁻⁷/° C., and particularly preferably −0.5×10⁻⁷/° C. to 0.5×10⁻⁷/° C.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, the thermal expansion coefficient at 30° C. to 750° C. is preferably 25×10⁻⁷/° C. or less, 23×10⁻⁷/° C. or less, 21×10⁻⁷/° C. or less, 20×10⁻⁷/° C. or less, 18×10⁻⁷/° C. or less, 16×10⁻⁷/° C. or less, 14×10⁻⁷/° C. or less, 12×10⁻⁷/° C. or less, 10×10⁻⁷/° C. or less, 9×10⁻⁷/° C. or less, 8×10⁻⁷/° C. or less, 7×10⁻⁷/° C. or less, 6×10⁻⁷/° C. or less, 5×10⁻⁷/° C. or less, 4×10⁻⁷/° C. or less, and particularly preferably 3×10⁻⁷/° C. or less. When dimensional stability and/or thermal shock resistance is specifically required, the thermal expansion coefficient at 30° C. to 750° C. is preferably −15×10⁻⁷/° C. to 15×10⁻⁷/° C., −12×10⁻⁷/° C. to 12×10⁻⁷/° C., −10×10⁻⁷/° C. to 10×10⁻⁷/° C., −8×10⁻⁷/° C. to 8×10⁻⁷/° C., −6×10⁻⁷/° C. to 6×10⁻⁷/° C., −5×10⁻⁷/° C. to 5×10⁻⁷/° C., −4.5×10⁻⁷/° C. to 4.5×10⁻⁷/° C., −4×10⁻⁷/° C. to 4×10⁻⁷/° C., −3.5×10⁻⁷/° C. to 3.5×10⁻⁷/° C., −3×10⁻⁷/° C. to 3×10⁻⁷/° C., −2.5×10⁻⁷/° C. to 2.5×10⁻⁷/° C., −2×10⁻⁷/° C. to 2×10⁻⁷/° C., −1.5×10⁻⁷/° C. to 1.5×10⁻⁷/° C., −1×10⁻⁷/° C. to 1×10⁻⁷/° C., and particularly preferably −0.5×10⁻⁷/° C. to 0.5×10⁻⁷/° C.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, the Young modulus is preferably 60 GPa to 120 GPa, 70 GPa to 110 GPa, and particularly preferably 80 GPa to 100 GPa. When the Youngs modulus is too low or too high, the glass is easily broken.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, the rigidity is preferably 25 GPa to 50 GPa, 27 GPa to 48 GPa, and particularly preferably 30 GPa to 45 GPa. When the rigidity is too low or too high, the glass is easily broken.

In the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention, the Poissons ratio is preferably 0.35 or less, 0.3 or less, and particularly preferably 0.25 or less. When the Poisson s ratio is too large, the glass is easily broken.

Next, a method for manufacturing the Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention will be described.

First, a raw material batch prepared so as to have a glass having the above composition is charged into a glass melting furnace, melted at 1,500° C. to 1,750° C., and then molded. When melting the glass, a flame melting method using a burner or the like, an electric melting method using electric heating, or the like may be used. It is also possible to melt by laser irradiation or by plasma.

Next, the obtained crystallizable glass (glass that can be crystallized) is subjected to a heat treatment to be crystallized. As crystallization conditions, first, nucleation is performed at 700° C. to 950° C. (preferably 750° C. to 900° C.) for 0.1 to 5 hours (preferably 1 to 3 hours), and then crystal growth is performed at 800° C. to 1,050° C. (preferably 800° C. to 1,000° C.) for 0.1 to 50 hours (preferably 0.2 to 10 hours). In this way, a transparent Li₂O—Al₂O₃—SiO₂-based crystallized glass in which the β-quartz solid solution crystal is precipitated as a main crystal can be obtained. Further, the heat treatment is performed at 950° C. to 1,200° C. for 0.5 to 5 hours to precipitate a β-spodumene solid solution crystal, and a white opaque LAS-based crystallized glass can be obtained.

EXAMPLES

Hereinafter, the present invention will be described based on Examples, but the present invention is not limited to the following Examples. Tables 1 to 4 show Examples (sample Nos. 1 to 9) and Comparative Examples (sample No. 10) of the present invention.

TABLE 1 No. 1 No. 2 No. 3 Composition SiO₂ 63.4 62.8 63.4 [wt %] Al₂O₃ 21.5 21.3 21.4 Li₂O 3.6 3.5 3.5 HfO₂ 5.1 0 5.0 Ta₂O₅ 0 6.2 0 Na₂O 0.4 0.4 0.4 K₂O 0.3 0.3 0.3 MgO 0.7 0.7 0.7 CaO 0 0 0 SrO 0 0 0 BaO 1.2 1.2 1.2 TiO₂ 0 0 0.5 ZrO₂ 2.2 2.1 2.1 P₂O₅ 1.4 1.3 1.3 SnO₂ 0.2 0.2 0.2 Fe₂O₃ 0.015 0.015 0.015 Transmittance [%] at 43 10 Unmeasured thickness of 3 mm and wavelength of 300 nm Precipitated crystal β-quartz solid β-quartz solid β-quartz solid solution solution solution Thermal expansion −0.2 −0.4 0 coefficient at 30° C. to 380° C. [×10⁻⁷/° C.] Thermal expansion 0.4 0.9 0.8 coefficient at 30° C. to 750° C. [×10⁻⁷/° C.] Youngs modulus 92 93 Unmeasured [GPa] Rigidity [GPa] 37 38 Unmeasured Poissons ratio 0.23 0.22 Unmeasured Appearance Colorless Colorless Colorless

TABLE 2 No. 4 No. 5 No. 6 Composition SiO₂ 65.2 63.6 66.2 [wt %] Al₂O₃ 22 22.5 23 Li₂O 3.7 4 2.7 HfO₂ 0.01 0.05 0.1 Ta₂O₅ 3.1 2.2 0 Na₂O 0.7 1.5 0.4 K₂O 0.3 0.1 0.3 MgO 0.7 1.1 0.7 CaO 0 0 0 SrO 0 0 0 BaO 1 0.4 1 TiO₂ 0 0 0 ZrO₂ 2.1 2.9 4.5 P₂O₅ 0.8 0.5 0.5 SnO₂ 0.4 1.1 0.6 Fe₂O₃ 0.015 0.015 0.015 Transmittance [%] at Unmeasured Unmeasured Unmeasured thickness of 3 mm and wavelength of 300 nm Precipitated crystal β-quartz solid β-quartz solid β-quartz solid solution solution solution Thermal expansion Unmeasured Unmeasured Unmeasured coefficient at 30° C. to 380° C. [×10⁻⁷/° C.] Thermal expansion Unmeasured Unmeasured Unmeasured coefficient at 30° C. to 750° C. [×10⁻⁷/° C.] Youngs modulus Unmeasured 92 Unmeasured [GPa] Rigidity [GPa] Unmeasured 37 Unmeasured Poissons ratio Unmeasured 0.23 Unmeasured Appearance Colorless Colorless Colorless

TABLE 3 No. 7 No. 8 No. 9 Composition SiO₂ 62.2 62.2 61.2 [wt %] Al₂O₃ 22.6 23.1 23 Li₂O 2.5 3.2 4.5 HfO₂ 0.5 1 0.05 Ta₂O₅ 4.5 0 1 Na₂O 0.4 0.8 0.4 K₂O 0.8 0.3 0.3 MgO 0 0.7 1.2 CaO 0 0.9 0 SrO 0 0.5 1.6 BaO 2 0 1.2 TiO₂ 0.2 0 0.02 ZrO₂ 2.5 3.8 3 P₂O₅ 1.6 3.2 1.8 SnO₂ 0.2 0.3 0.7 Fe₂O₃ 0.015 0.015 0.015 Transmittance [%] at Unmeasured Unmeasured Unmeasured thickness of 3 mm and wavelength of 300 nm Precipitated crystal β-quartz solid β-quartz solid β-quartz solid solution solution solution Thermal expansion Unmeasured Unmeasured Unmeasured coefficient at 30° C. to 380° C. [×10⁻⁷/° C.] Thermal expansion Unmeasured Unmeasured Unmeasured coefficient at 30° C. to 750° C. [×10⁻⁷/° C.] Youngs modulus Unmeasured Unmeasured Unmeasured [GPa] Rigidity [GPa] Unmeasured Unmeasured Unmeasured Poissons ratio Unmeasured Unmeasured Unmeasured Appearance Colorless Colorless Colorless

TABLE 4 No. 10 Composition SiO₂ 66.7 [wt %] Al₂O₃ 22.2 Li₂O 3.7 HfO₂ 0 Ta₂O₅ 0 Na₂O 0.4 K₂O 0.3 MgO 0.7 CaO 0 SrO 0 BaO 1.2 TiO₂ 1.8 ZrO₂ 2.8 P₂O₅ 0 SnO₂ 0.2 Fe₂O₃ 0.015 Transmittance [%] at thickness of 0 3 mm and wavelength of 300 nm Precipitated crystal β-quartz solid solution Thermal expansion coefficient −1.3 at 30° C. to 380° C. [×10⁻⁷/° C.] Thermal expansion coefficient 1.3 at 30° C. to 750° C. [×10⁻⁷/° C.] Youngs modulus [GPa] 92 Rigidity [GPa] 38 Poissons ratio 0.21 Appearance Yellow

First, each raw material was mixed in the form of oxide, hydroxide, carbonate, nitrate or the like so as to obtain a glass having the compositions shown in Tables 1 to 4, and a glass batch was obtained. The obtained glass batch was charged into a crucible made of reinforced platinum and was melted at 1,680° C. for 20 hours. After melting, the glass was rolled to a thickness of 4 mm and further cooled to room temperature using a slow cooling furnace to obtain a crystallizable glass.

The crystallizable glass was subjected to a heat treatment at 750° C. to 900° C. for 1.5 hours to form nuclei, and then further subjected to a heat treatment at 800° C. to 1,000° C. for 4 hours to be crystallized. The obtained crystallized glass was evaluated for the transmittance, the precipitated crystal, the thermal expansion coefficient, the Youngs modulus, the rigidity, the Poissons ratio, and the appearance.

The transmittance was evaluated by a transmittance at a wavelength of 300 nm measured with a spectrophotometer for a crystallized glass plate whose two sides were optically polished to a wall thickness of 3 mm. A spectrophotometer V-670 manufactured by JASCO Corporation was used in the measurement.

The precipitated crystal was evaluated using an X-ray diffractometer (fully automatic multipurpose horizontal X-ray diffractometer Smart Lab, manufactured by Rigaku Corporation).

The thermal expansion coefficient was evaluated by an average linear thermal expansion coefficient measured in the temperature ranges of 30° C. to 380° C. and 30° C. to 750° C. using a crystallized glass sample processed to 20 mm×3.8 mm (diameter). Diatometer manufactured by NETZSCH was used in the measurement.

The Youngs modulus, the rigidity, and the Poissons ratio were measured in a room temperature environment using a free resonance type elastic modulus measuring device for a plate-shaped sample (40 mm×20 mm×20 mm) whose surface was polished with a polishing solution in which No. 1200 alumina powder was dispersed.

The appearance was evaluated by visually confirming the color tone of the crystallized glass.

As is clear from Tables 1 and 2, the crystallized glasses of sample Nos. 1 to 9, which are Examples, have a colorless appearance, high transmittance, and a thermal expansion coefficient of almost 0. It is also found that Youngs modulus, the rigidity, and the Poissons ratio are desired values and the crystallized glasses are not easily broken. The crystallized glass of sample No. 10, which is Comparative Example, has a yellow appearance and a low transmittance of 0%, and has an absolute value of the thermal expansion coefficient larger than that of Examples.

INDUSTRIAL APPLICABILITY

The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to the present invention is suitable for front windows of oil stoves or wood stoves, substrates for high-tech products such as substrates for color filters and image sensors, setters for firing electronic components, light diffusers, core tubes for semiconductor manufacturing, semiconductor manufacturing masks, optical lenses, dimensional measurement members, communication members, building members, chemical reaction containers, top plates for electromagnetic cooking, and window glass for fire doors. 

1: A Li₂O—Al₂O₃—SiO₂-based crystallized glass comprising: in a mass basis, SnO₂: 0% to 5%; and HfO₂+Ta₂O₅: 0.01% to 10%. 2: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, further comprising: in a mass basis, SiO₂: 40% to 90%; Al₂O₃: 5% to 30%; Li₂O: 1% to 10%; SnO₂: 0.01% to 5%; and HfO₂+Ta₂O₅: 0.01% to 10%. 3: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, further comprising: in a mass basis, SiO₂: 40% to 90%; Al₂O₃: 5% to 30%; Li₂O: 1% to 10%; SnO₂: 0.01% to 5%; and HfO₂+Ta₂O₅: 0.05% to 10%. 4: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, further comprising: in a mass basis, Na₂O: 0% to 10%; K₂O: 0% to 10%; MgO: 0% to 10%; CaO: 0% to 10%; SrO: 0% to 10%; BaO: 0% to 10%; ZnO: 0% to 10%; P₂O₅: 0% to 5%; TiO₂: 0% to 2%, and ZrO₂: 0% to 10%. 5: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, wherein an appearance thereof is colorless and transparent. 6: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, wherein a transmittance thereof at a thickness of 3 mm and a wavelength of 300 nm is 10% or more. 7: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, wherein a β-quartz solid solution is precipitated as a main crystal. 8: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, wherein a thermal expansion coefficient thereof at 30° C. to 380° C. is 20×10⁻⁷/° C. or less. 9: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 1, wherein a thermal expansion coefficient thereof at 30° C. to 750° C. is 25×10⁻⁷/° C. or less. 10: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 2, further comprising: in a mass basis, SiO₂: 40% to 90%; Al₂O₃: 5% to 30%; Li₂O: 1% to 10%; SnO₂: 0.01% to 5%; and HfO₂+Ta₂O₅: 0.05% to 10%. 11: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 2, further comprising: in a mass basis, Na₂O: 0% to 10%; K₂O: 0% to 10%; MgO: 0% to 10%; CaO: 0% to 10%; SrO: 0% to 10%; BaO: 0% to 10%; ZnO: 0% to 10%; P₂O₅: 0% to 5%; TiO₂: 0% to 2%, and ZrO₂: 0% to 10%. 12: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 3, further comprising: in a mass basis, Na₂O: 0% to 10%; K₂O: 0% to 10%; MgO: 0% to 10%; CaO: 0% to 10%; SrO: 0% to 10%; BaO: 0% to 10%; ZnO: 0% to 10%; P₂O₅: 0% to 5%; TiO₂: 0% to 2%, and ZrO₂: 0% to 10%. 13: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 10, further comprising: in a mass basis, Na₂O: 0% to 10%; K₂O: 0% to 10%; MgO: 0% to 10%; CaO: 0% to 10%; SrO: 0% to 10%; BaO: 0% to 10%; ZnO: 0% to 10%; P₂O₅: 0% to 5%; TiO₂: 0% to 2%, and ZrO₂: 0% to 10%. 14: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 2, wherein an appearance thereof is colorless and transparent. 15: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 3, wherein an appearance thereof is colorless and transparent. 16: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 2, wherein a transmittance thereof at a thickness of 3 mm and a wavelength of 300 nm is 10% or more. 17: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 3, wherein a transmittance thereof at a thickness of 3 mm and a wavelength of 300 nm is 10% or more. 18: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 2, wherein a β-quartz solid solution is precipitated as a main crystal. 19: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 2, wherein a thermal expansion coefficient thereof at 30° C. to 380° C. is 20×10⁻⁷/° C. or less. 20: The Li₂O—Al₂O₃—SiO₂-based crystallized glass according to claim 2, wherein a thermal expansion coefficient thereof at 30° C. to 750° C. is 25×10⁻⁷/° C. or less. 